Loss of separation between aircraft can occur whenever specified separation requirements between the aircraft are breached. Minimum separation standards for airspace are specified by Air Traffic Services (ATS) authorities, based on FAA (Federal Aviation Administration) standards.
When a potential loss of separation (LOS) is detected, the LOS may be addressed by human intervention. For example, a traffic controller may predict the loss of separation and may provide instruction to one or more of the vehicles to avoid the LOS. However, neither a traffic controller nor a remote pilot can enable an on-board capability to avoid other aircraft when a data link of an unmanned aerial vehicle fails.
In another example, a Traffic Alert and Collision Avoidance System (TCAS) may predict an unsafe separation and may generate either an alert or an avoidance instruction to a vehicle controller to change altitude. Air traffic rules indicate that unmanned systems disallow altitude changes for separation of unmanned aircraft. For example, FAA CFR 91.113 (b) states: “When a rule of this section gives another aircraft the right-of-way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear.”